Emerging wireless networks have evolved to support and provide high spectral efficiency modulation techniques such as quadrature modulation (QAM) combined with orthogonal frequency division multiplexing (OFDM). These modulated communication signals include high peak-to-average power ratio (PAPR) signals. In addition, next generation wireless standards such as long-term evolution advanced (LTE-A) support a wide frequency spectrum allocation and carrier aggregation (CA) techniques to further extend the signal bandwidth. Therefore, operating at higher data rates with wideband signals in a high power amplifier (PA) requires highly linear and efficient signal transmission.
To transmit successful amplification of intra-band inter-band CA signals in contiguous or non-contiguous modes, high linearity requirements warrant increasing the instantaneous bandwidth (IBW) of the PA. Furthermore, when wideband OFDM signals in concurrent mode are transmitted through a high power PA, severe electrical memory effects and inter-modulation distortion (IMD) may result. These distortions present limitations to digital predistortion (DPD) linearization.
In fifth generation (5G) systems, transmitters require spectrum efficiency enhancement using massive multiple-input multiple-output (MIMO) techniques and need a large number of PAs. In addition, 5G DPD systems require high linearization capacity and implementation complexity to optimize the efficiency-linearity of a PA. To reduce power consumption and size of DPD systems, low-complexity DPD solutions are desirable. Accordingly, it is also desirable to design high efficiency PAs with minimal distortions.